A variety of systems for providing windshield defrosting in aircraft have heretofore been suggested and/or utilized. For example, the Bell 206 helicopter has been in production since 1963. The windshield defroster system for this helicopter consists of vane axial type blowers connected to polycarbonate air dispersal shrouds.
The function of the blowers is to circulate cabin air across the windshield. There is no direct heat source for this system.
The Bell 206 windshield is particularly difficult to defrost because of its large surface area and because it is located so far forward from the cabin heater outlets. The manufacturer's defroster design is a compromise which is only partially effective.
Experience has shown this defroster system to be ineffective when the cabin air temperature is initially cold, and marginally effective when the cabin air temperature is warm. Furthermore, the circulation blowers are expensive, very noisy, and have limited service life.
Based on a review of the Federal Aviation Administration document "Summary of Supplemental Type Certificates" (any design changes to the helicopter, not incorporated by the manufacturer, must be FAA approved under authority of a supplemental type certificate) and based on common knowledge in the industry it is felt that there is no engine bleed air type defroster system of the type herein suggested available for the Bell 206 helicopter.
This invention is intended to be used in conjunction with the existing air dispersal shroud on aircraft such as the Bell 206 helicopter. The blower may be retained or discarded.